Chapter 1: Introduction to DBMS
Introduction to DBMS
DBMS stands for Database Management System. We can break it like this DBMS =
Database + Management System. Database is a collection of data and Management
System is a set of programs to store and retrieve those data. Based on this we can
define DBMS like this: DBMS is a collection of inter-related data and set of programs to
store & access those data in an easy and effective manner.
Drawbacks of File system
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● Data redundancy: Data redundancy refers to the duplication of data, lets say we
are managing the data of a college where a student is enrolled for two courses, the
same student details in such case will be stored twice, which will take more storage
w
than needed. Data redundancy often leads to higher storage costs and poor access
time.
ut
● Data inconsistency: Data redundancy leads to data inconsistency, lets take the
same example that we have taken above, a student is enrolled for two courses and
we have student address stored twice, now lets say student requests to change his
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address, if the address is changed at one place and not on all the records then this
can lead to data inconsistency.
● Data Isolation: Because data are scattered in various files, and files may be in
a
different formats, writing new application programs to retrieve the appropriate data
is difficult.
k
● Dependency on application programs: Changing files would lead to change in
an
application programs.
● Atomicity issues: Atomicity of a transaction refers to “All or nothing”, which means
either all the operations in a transaction executes or none.
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For example: Lets say Steve transfers 100$ to Negan’s account. This transaction
consists multiple operations such as debit 100$ from Steve’s account, credit 100$
Pr
to Negan’s account. Like any other device, a computer system can fail lets say it
fails after first operation then in that case Steve’s account would have been debited
by 100$ but the amount was not credited to Negan’s account, in such case the
rollback of operation should occur to maintain the atomicity of transaction. It is
difficult to achieve atomicity in file processing systems.
● Data Security: Data should be secured from unauthorised access, for example a
student in a college should not be able to see the payroll details of the teachers,
such kind of security constraints are difficult to apply in file processing systems.
Advantage of DBMS over file system
There are several advantages of Database management system over file system. Few of
, inconsistency is data redundancy, since data normalization takes care of the data
redundancy, data inconsistency also been taken care of as part of it
● Data Security: It is easier to apply access constraints in database systems so that
only authorized user is able to access the data. Each user has a different set of
access thus data is secured from the issues such as identity theft, data leaks and
misuse of data.
● Privacy: Limited access means privacy of data.
● Easy access to data – Database systems manages data in such a way so that the
data is easily accessible with fast response times.
● Easy recovery: Since database systems keep the backup of data, it is easier to do
a full recovery of data in case of a failure.
● Flexible: Database systems are more flexible than file processing systems.
Database Applications
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● Banking: all transactions
● Airlines: reservations, schedules
● Universities: registration, grades
● Sales: customers, products, purchases
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● Online retailers: order tracking, customized recommendations
● Manufacturing: production, inventory, orders, supply chain
● uman resources: employee records, salaries, tax deductions
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Disadvantages of DBMS
● DBMS implementation cost is high compared to the file system
● Complexity: Database systems are complex to understand
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● Performance: Database systems are generic, making them suitable for various
k
applications. However this feature affects their performance for some applications.
Data Abstraction in DBMS
an
Database systems are made-up of complex data structures. To ease the user interaction
with database, the developers hide internal irrelevant details from users. This process of
hiding irrelevant details from user is called data abstraction.
iy
Pr
Introduction to DBMS
DBMS stands for Database Management System. We can break it like this DBMS =
Database + Management System. Database is a collection of data and Management
System is a set of programs to store and retrieve those data. Based on this we can
define DBMS like this: DBMS is a collection of inter-related data and set of programs to
store & access those data in an easy and effective manner.
Drawbacks of File system
ad
● Data redundancy: Data redundancy refers to the duplication of data, lets say we
are managing the data of a college where a student is enrolled for two courses, the
same student details in such case will be stored twice, which will take more storage
w
than needed. Data redundancy often leads to higher storage costs and poor access
time.
ut
● Data inconsistency: Data redundancy leads to data inconsistency, lets take the
same example that we have taken above, a student is enrolled for two courses and
we have student address stored twice, now lets say student requests to change his
kh
address, if the address is changed at one place and not on all the records then this
can lead to data inconsistency.
● Data Isolation: Because data are scattered in various files, and files may be in
a
different formats, writing new application programs to retrieve the appropriate data
is difficult.
k
● Dependency on application programs: Changing files would lead to change in
an
application programs.
● Atomicity issues: Atomicity of a transaction refers to “All or nothing”, which means
either all the operations in a transaction executes or none.
iy
For example: Lets say Steve transfers 100$ to Negan’s account. This transaction
consists multiple operations such as debit 100$ from Steve’s account, credit 100$
Pr
to Negan’s account. Like any other device, a computer system can fail lets say it
fails after first operation then in that case Steve’s account would have been debited
by 100$ but the amount was not credited to Negan’s account, in such case the
rollback of operation should occur to maintain the atomicity of transaction. It is
difficult to achieve atomicity in file processing systems.
● Data Security: Data should be secured from unauthorised access, for example a
student in a college should not be able to see the payroll details of the teachers,
such kind of security constraints are difficult to apply in file processing systems.
Advantage of DBMS over file system
There are several advantages of Database management system over file system. Few of
, inconsistency is data redundancy, since data normalization takes care of the data
redundancy, data inconsistency also been taken care of as part of it
● Data Security: It is easier to apply access constraints in database systems so that
only authorized user is able to access the data. Each user has a different set of
access thus data is secured from the issues such as identity theft, data leaks and
misuse of data.
● Privacy: Limited access means privacy of data.
● Easy access to data – Database systems manages data in such a way so that the
data is easily accessible with fast response times.
● Easy recovery: Since database systems keep the backup of data, it is easier to do
a full recovery of data in case of a failure.
● Flexible: Database systems are more flexible than file processing systems.
Database Applications
ad
● Banking: all transactions
● Airlines: reservations, schedules
● Universities: registration, grades
● Sales: customers, products, purchases
w
ut
● Online retailers: order tracking, customized recommendations
● Manufacturing: production, inventory, orders, supply chain
● uman resources: employee records, salaries, tax deductions
kh
Disadvantages of DBMS
● DBMS implementation cost is high compared to the file system
● Complexity: Database systems are complex to understand
a
● Performance: Database systems are generic, making them suitable for various
k
applications. However this feature affects their performance for some applications.
Data Abstraction in DBMS
an
Database systems are made-up of complex data structures. To ease the user interaction
with database, the developers hide internal irrelevant details from users. This process of
hiding irrelevant details from user is called data abstraction.
iy
Pr
